Field of the Invention
The present invention relates to a technique of shortening a period to transition from a power saving state to an operational state in an apparatus having a main system and a sub-system.
Description of the Related Art
With an objective of shortening a transition period (hereinafter, referred to as a recovery period) when causing an apparatus, which is divided into a main system and a sub-system, to transition from a power saving state to an operational state, there is a technique of notifying a recovery period of the sub-system to the main system (Japanese Patent Laid-Open No. 2014-182801). According to Japanese Patent Laid-Open No. 2014-182801, because the main system can start accessing the sub-system by waiting for just the notified recovery period, it is possible to shorten the recovery period.
However, in the technique recited in Japanese Patent Laid-Open No. 2014-182801, the sub-system only notifies a single recovery period. However, if the sub-system has multiple functions, a plurality of power states may be held in the power saving state, and recovery periods in each of the power states may be different. In other words, if it only possible to notify the one longest recovery period as in Japanese Patent Laid-Open No. 2014-182801, even if the sub-system is in a power state having a shorter recovery period in the power saving state, it is not possible to access the sub-system without waiting for the longer time period. With this arrangement, there is a problem that the recovery to the operational state of the apparatus is slower than it needs to be.